In the past two decades numerous technological advances in the medical and biological arts have prompted a better understanding of the micro-universe, or that which cannot be seen with the naked eye. Methods are known for calibrating and characterizing apertures in the range between 0.1 micron (.mu.) to 10.mu. (1000 Angstroms (.ANG.) to 100,000 .ANG. where 1.mu.=10,000 .ANG.).
This range covers the sizes and shapes of most bacteria, such as Rickettside and Mycoplasma sp. (1000-3000 .ANG.), Hemophilus influenzae (2000-3000 .ANG.,.times.5000-20,000 .ANG.), Escherichia coli (5000.times.10,000-30,000 .ANG.) Bacillus anthracis (10,000-13,000.times.30,000-100,000 .ANG.) and also blood cells (.about.700,000 .ANG.). In comparison, the limit of human vision is about 400,000 .ANG..
These known methods, however, are unsatisfactory for calibrating and characterizing even smaller apertures, such as those having diameters from 0.1.mu.(.about.1000 .ANG.) to 0.001.mu.(10 .ANG.). Within this size range are measured discrete biological particles including viruses such as Reo virus and the pathenogenic Poliomyelitis virus responsible for polio (.about.310 .ANG.); the stunted bean virus (.about.200 .ANG.); the influenza virus (.about.1000 .ANG.); important proteins such as insulin (diameter .about.50-60 .ANG.); the oxygen-carrying hemoglobin molecule found in blood cells (diameter .about.80-100 .ANG.); .beta.-lipoproteins (diameter.about.200 .ANG.) and other diverse subcellular components such as biological channels made of membrane proteins which allow nutrients, ions and other essential materials into plant or animal cells. Such membrane proteins are discussed in N. Urwin and R. Henderson, (Feb. 1984), The Structure of Proteins in Biological Membranes, Scientific American, pp. 78-94.
Present techniques for calibrating or measuring the apertures of such channels have met with only limited success because of the difficulty of designing a spherical structure as small as, for example, a cell channel (.about.15-20 .ANG.). For example, such known processes employ structures which are random coiled and tend to reptate or unravel when contacted with an aperture of a size smaller than the measuring structure. This reptating or unraveling of these measuring structures, in turn, induces tremendous variations in measurements, requiring weeks and even months to perform. Such known measuring structures include nonspherical, low molecular weight compounds and proteins. For example, dextrans, a type of low molecular weight sugar, are subject to reptating motions through a pore whose dimensions are smaller than that of the dextran molecule. The dextran molecule uncoils and "snakes" through. The use of such deformable molecules as probes leads to serious doubt as to the validity of the measured molecular diameters.
Thus, it would be highly desirable to provide a precise, accurate and reliable process for calibrating and characterizing substances having submicron apertures.